MEASURING INSTRUMENT FOR THE DETERMINATION OF THE PARTIAL PRESSURE OF OXYGEN AND CARBON DIOXIDE AND OF THE pH VALUE OF A BLOOD SAMPLE

ABSTRACT

A measuring instrument and system for the determination of the partial oxygen and carbon dioxide pressures and of the pH value of a blood test sample having a thermostatized measuring vessel with a measuring capillary tube inserted therein to contain the blood test sample with three receiving bores in the measuring vessel and three measuring electrode units one of which being oxygen sensitive with the second carbon dioxide sensitive and the third being pH sensitive. Each of the measuring sensors are in contact with the said blood test sample and a measuring and recording device for electrode conductively connected with one of the measuring electrode units with a conical receiving bore provided on the measuring vessel. Three control bores terminate in the conical receiving bore and a switch element is inserted in the receiving bore to register with the control bores in three different positions with a pumping device providing for alternate suction and delivery strokes and a pipeline connects the pumping device with the control bores. A gas intake pipe connects the pressure tank with the second control bore and a suction pump and a suction pipe connect the latter with the third control bore and a conical filler connection is mounted on the measuring vessel and is connected with the extremity of the measuring capillary tube opposite the switch member.

Unite States Patent Harnoncourt [54] MEASURING INSTRUMENT FOR THEDETERMINATION OF THE PARTIAL PRESSURE OF OXYGEN AND CARBON DIOXIDE ANDOF THE PH VALUE OF A BLOOD SAMPLE [72] Inventor:

[73] Assignee: Hans List, Graz, Austria [22] Filed: Apr. 22, 1969 [2]]Appl. No.: 818,288

Karl Harnoncourt, Graz, Austria Feb. 1, 1972 Primary ExaminerMichael J.Lynch Attorney-Watson, Cole, Grindle & Watson [5 7] ABSTRACT A measuringinstrument and system for the determination of the partial oxygen andcarbon dioxide pressures and of the pH value of a blood test samplehaving a thermostatized measuring vessel with a measuring capillary tubeinserted thereinto contain the blood test sample with three receivingbores in the measuring vessel and three measuring electrode units one ofwhich being oxygen sensitive with the second carbon dioxide sensitiveand the third being pH sensitive. Each of the measuring sensors are incontact with the said blood test sample and a measuring and recordingdevice for electrode conductively connected with one of the measuringelectrode units with a conical receiving bore provided on the measuringvessel. Three control bores terminate in the conical receiving bore anda switch element is inserted in the receiving bore to register with thecontrol bores in three different positions with a pumping deviceproviding for alternate suction and delivery strokes and a pipelineconnects the pumping device with the control bores. A gas intake pipeconnects the pressure tank with the second control bore and a suctionpump and a suction pipe connect the latter with the third control boreand a conical filler connection is mounted on the measuring vessel andis connected with the extremity of the measuring capillary tube oppositethe switch member.

2 Claims, 2 Drawing Figures MEASURING INSTRUMENT EOE 'llllllEDETERMINATION OF THE PARTIAL PRESSURE OF OXYGEN AND CARBON DHOXTDE ANDOF THE PH VALUE OF A BLOOD SAMPLE This invention relates to a measuringinstrument for the determination of the partial pressures of oxygen andcarbon dioxide and of the pH value of a blood test sample contained in ameasuring capillary tube inside a thermostatized vessel by means ofthree measuring electrode units connected to a measuring and recordinginstrument, one of which comprises an oxygen-sensitive, the other acarbon-dioxide-sensitive, and the third a pl-l-sensitive sensor, thesaid sensors being in contact with the blood test sample.

Determinations of the partial oxygen and carbon dioxide pressures aswell as of the pH value of a blood test sample are essential operationsof the blood microanalysis procedure which is a method of clinicalexamination of considerable importance for the diagnosis of ailments ofthe heart, the lungs or of metabolic diseases and distinguishes itselfin particular by the fact that very small quantities of blood (about twoto three drops) only are required for the measurements. in addition tothe determination of the aforementioned values, microanalysis of theblood also includes the determination of other characteristic valuesnomographically ascertainable from the said measurements, such as thedetermination of the bicarbonate content of the blood test sample.

Before the measurements are carried out, the measuring capillary tubeand the chambers and cavities of the measuring container communicatingwith same should first be cleaned and dried and the measuring electrodestested at certain intervals of time by means of thermostatized andsteam-saturated test gases and buffer solutions. After the recordinginstrument has been properly readjusted, if necessary, the blood testsample, mixed with an anticoagulation agent and preserved in a tube isintroduced into the measuring capillary tube, whereupon the measuringand recording instrument is switched on. In order to obtain the bestresults from the measurements of the partial pressures, the bloodcontained in the measuring capillary tube'should be moved to and fro infront of the electrodes by means of a pumping comprising a pumpcommunicating in any suitable way with the measuring capillary tube andalternatingly producing a vacuum or overpressure. Following the readingof the partial oxygen and/or carbon dioxide pressures shown on therecording instrument it will be necessary to clean and dry the measuringcapillary tube preferably by introducing distilled water and byconnecting the other end of the measuring capillary tube to a suctionpump. For measuring the pH value an electrolytic connection to areference electrode has to be established. For extremely accurateexaminations the three most important pH values of the measured bloodtest sample are as follows:

I. The so-called actual pH value of the unaltered blood test sample,

2. the pH value following the balancing of the blood test sample with atest gas having a low partial carbon dioxide ressure,

3. the pH value following the balancing of the blood test sample with atest gas having a high partial carbon dioxide pressure.

In view of the log. function between p.CO and the pH value, the valuesthus measured permit, in a manner known per se, further nomographicevaluations and readings of additional informations, such asbicarbonate, p.CO etc.

The procedure of obtaining the proper balance of partial pressuresbetween the test gas and the blood test sample is termed equilibration.

The apparatus formerly used for carrying out microanalyses of the bloodare of a relatively complicated construction calling for the use ofhighly skilled operators and requiring an extremely concentrated effortin operation, if the measurements are to produce useful results, or elsesimplication of certain procedures can be achieved only at the expenseof the accuracy of the measurements.

In particular, equilibration by means of two test gases with a knowncarbon dioxide content with the conventional equipment available requireparticular attention and skill on the part of the operator and tiresomecleaning procedures following each measurement. Owing to these facts andto the numerous sources of error leading to absolutely meaninglessmeasuring results as a result of even minor mistakes on the part of theoperator, a prejudice against this method of measurement has developedamong experts, preventing the general use and propagation of thisvaluable means of diagnosis.

It is the object of the invention to provide a measuring apparatus ofthe type referred to above which permits avoidance of the shortcomingsof conventional equipment and will produce dependable results at greaterspeed of the measuring operations. For the purpose, according to theinvention, the three sensors are all accommodated in a common measuringcontainer and communicate with the measuring capillary tube through anaperture provided in the said capillary tube for each of the saidsensors, a switchover cock being provided at one end of the measuringcapillary tube, by means of which the measuring capillary tube can beattached as required to such connections as are provided on thecontainer for test gas feed pipes, a pumping device with alternatingsuction and delivery strokes and a suction pump. Thus the operationalsteps required for the determination of the partial oxygen and carbondioxide pressures as well as of the pH value can be performed in rapidsuccession and concentrated upon the narrow space of the thermostatizedcontainer. At the same time, sources of individual errors liable todistort the results of the measurements are practically eliminated bythe simple and largely mechanized operation of the instrument.

In view of these features, the measuring instrument according to theinvention is particularly suitable for semior fully automatic operationwith the use of a corresponding program control. This can be used bothfor the switchover of the recording instrument from one measuringelectrode to the other, for the operation of the pumping device and ofthe suction pump as well as for the actuation of a switchover cockoperated by a rotary magnet by means of appropriately timed switchpulses.

According to a preferred embodiment of the invention, the end of themeasuring capillary tube opposite the switchover cock is designed as aconical filler vent destined to receive the blood test sample or amixing hopper. Such an instrument is suitable not only for thedetermination of the aforesaid partial pressures and of the actual pHvalue but also for the special operation of the microanalysis of theblood gas termed equilibration. In order to initiate this operationalstep it is only necessary to place the switchover cock in a positionwhere the measuring capillary tube communicates with the requiredcalibration gas feed pipe. The test gas flowing into the measuringcapillary tube then forces the blood test sample into the mixing funnel,if provided, wherein the blood test sample is subsequently enriched withtest gas. The mixing hopper can be conveniently cleaned after removingit from the measuring head. When one-way mixing hoppers are used nocleaning is required at all.

Further details of the invention will appear from the followingdescription of an embodiment of the invention with reference to theaccompanying schematic drawings of the measuring instrument wherein:

HO. 1 is a longitudinal cross-sectional view of a measuring instrumentaccording to the invention; and

H6. 2 a partially sectional top view of the instrument shown in FlG. l.

The measuring container of the instrument is designed as a hollowcylindrical glass flask 2 arranged in a horizontal position and tightlyclosed at both ends by means of caps l. The glass flask 2 whoselongitudinal extension is shown as being interrupted in the drawing istilled with a liquid which is maintained at an approximate temperatureof about 37 C. by thermostat, so as to provide conditions similar to thebody temperature during the measurements.

Sealed into the glass flask 2 is a measuring capillary tube 3 extendingin the longitudinal direction of the flask, the two ends of the saidmeasuring capillary tube terminating in a flared-out aperture 4 leadingto the upper side of the glass flask 2. From the measuring capillarytube 3 extend apertures 5 destined to receive the measuring electrodes11, 12 and 13. The electrode 11 is oxygen sensitive, the electrode 12carbon dioxide sensitive and the electrode 13 pH value sensitive. Theelectrodes are connected to an electric measuring and recording device17 by means of connecting lines l4, l5 and l6. With the three electrodes(0 CO pH) installed in place, the measuring sensors are located in thelumen of the measuring capillary tubes 3, the fourth aperture beingdesigned to produce the electrolytic bridge leading to the referenceelectrode.

As illustrated on the left side of the drawing, in the flaredoutaperture 4 of the measuring capillary tube 3 a roughly sketchedswitchover cock 6 with a control knob 7 is inserted. In this aperture 4three of connecting lines 8, 8' and 8" terminate, of which line 8 isconnected to a pumping device 18 with alternating suction and deliverystrokes, line 8 to a source 19 of test gas and line 8 to a suction pump.Depending on requirements, the measuring capillary tube 3 can be eitherimpinged upon by test gases of different carbon dioxide and oxygencontents from the source 19 of test gases by appropriately setting theswitchover cock 6 or else connected to the device 18 or the suction pump20. These auxiliary devices are in permanent communication viaappropriate lines with the measuring system.

For the purpose of equilibration, a mixing hopper 9 with its cover ontop, can be inserted with a tight fit into the flaredout aperture 4 ofthe measuring capillary tube 3 opposite the switchover cock 6, as shownin the drawing. With the mixing hopper 9 removed, the right-handaperture 4 of the measuring capillary tube 3 defines the tiller vent forreceiving the blood test sample.

At the beginning of the measurement, the measuring capillary tube 3 iswashed with distilled water and dried in a manner not to be described atany length here. If required, the measuring electrodes inserted in thereceiving apertures 5 are subsequently checked, the switchover cock 6being placed in a switch position where a thermostatized andsteam-saturated test gas enters the measuring capillary tube 3 throughone of the pipe 8. After the recording instrument connected to themeasuring electrodes l1, 12, 13 has been corrected, if necessary, themeasuring operation proper can be started. Now the blood test sample isintroduced into the measuring capillary tube 3 through the filler vent 4and after the electrolytic bridge leading to the reference electrode hasbeen produced, the reading of the pH value is first obtained from themeasuring instrument. Then the switchover cock 6 is placed in a positionwhere the measuring capillary tube 3 is connected to the pumping device18. By the alternating suction-and-pressure effect of the pumping devicea reciprocating movement is imparted to the blood test sample in themeasuring capillary tube. Now the partial oxygen pressure'and thepartial carbon dioxide pressure of the blood test sample can be read onthe recording instrument l7 and duly recorded. Upon completion of themeasuring operation, the measuring capillary tube is again cleaned anddried, while being connected to the suction pump 20 of the measuringsystem by means of the switchover cock 6 and the line 8 The theequilibration of a blood test sample contained in the measuringcapillary tube 3, the mixing hopper 9 is inserted in the aperture 4 andby means of the switchover cock placed in an appropriate position, atest gas of a determined carbon dioxide concentration is introduced intothe measuring capillary tube 3 which causes the blood to rise in themixing hopper wherein the blood test sample is intimately mixed with thetest gas under continuous formation of bubbles, so that the blood testsample assumes the same exactly defined carbon dioxide partial pressureof the test gas. After the gas flow has been stopped by means of theswitchover cock 6, the equilibrated blood is drawn back by capillaryaction from the hopper 9 into the measuring capillary tube 3 where thepH value is again measured. Equilibration with the second test gas andthe subsequent third pH measurement are carried out in a similar manner,whereupon the hopper 9 is removed and the measuring capillary tubewashed and dried so as to be ready for the next measuring operation.

Iclaim:

l. A measuring instrument for the determination of the partial oxygenand carbon dioxide pressures and of the pH value of a blood test sample,comprising a thermostated measuring vessel, a measuring capillary tubelightly inserted in said measuring vessel and containing said blood testsample, three receiving bores terminating in said measuring capillarytube, three measuring electrode units, a first of said units comprisingan oxygen-sensitive measuring sensor, the second of said unitscomprising a carbon-dioxide-sensitive measuring sensor, and the third ofsaid units comprising a pH-sensitive measuring sensor, each of saidmeasuring sensors inserted in a respective one of said receiving boresand being in contact with said blood test sample, a measuring andrecording device, means to selectively connect said measuring andrecording device to one of said measuring electrode units, a conicalreceiving bore provided on said measuring vessel and connected to oneend of said measuring capillary tube, three control bores terminating insaid conical receiving bore, a switchcock inserted in said receivingbore and registering with one of said control bores in each of threedifferent switch positions, a pumping device with alternating suctionand delivery strokes, a pipeline connecting said pumping device with oneof said control bores, a pressure tank containing a test gas, a gasintake pipe connecting said pressure tank with a second one of saidcontrol bores, a suction pump, a suction pipe connecting said suctionpump with a third one of said control bores, and a conical fillerconnection method on said measuring vessel and connected with the otherend of the measuring capillary tube opposite the switchcock.

2. A measuring instrument according to claim 5, comprising a mixinghopper insertable in the said conical filler connection of the measuringvessel.

2. A measuring instrument according to claim 5, comprising a mixinghopper insertable in the said conical filler connection of the measuringvessel.